Such files can be saved, for instance by the geometry optimization program, and reused
later to recover a certain optimized geometry. The format of the input in filename
is the same as for ordinary input.

If option=NOINDEX|IGNOREINDEX is given then variable indices are ignored and only
the last value saved is read (without index). This can be useful if for example a file
saved with SAVEACT in a geometry optimization is read, and it is intended to
continue with the variables that were saved last.